The sunburn you can't feel is aging your skin

Sunlight carries two kinds of ultraviolet rays, and they do very different damage. UVB is the burner — it's strongest midday, causes red sunburns, and is the main trigger behind most skin cancers. UVA is the sneaky one: it's present all day, penetrates deeper into the skin, and drives most photoaging — wrinkles, leathery texture, and dark spots — while also contributing to cancer risk. You never feel UVA the way you feel a burn, which is exactly why it's easy to underestimate.

Here's the twist most people miss: ordinary window glass blocks most UVB but lets much of the UVA through. That's why long-term drivers and people who sit by sunny windows often show more sun damage on the side of the body facing the glass. Clouds don't save you either — a large fraction of UV passes straight through overcast skies, so damage accumulates on gray days too.

This is where SPF misleads people. The SPF number measures only UVB protection, so a high-SPF product can still leave your skin exposed to UVA. The fix is looking for the words broad spectrum, which means the sunscreen is tested to block both. Because UV exposure is cumulative over a lifetime, the incidental doses — commutes, walks, sitting near a window — add up more than the occasional beach day.